I bought a soft case that velcros to the stem. It works really well. Water proof, decent shock protection, clear plastic screen you can use the touch screen without unzipping it. It's made by Handy Andy. Only cost like $20 I bought it through my LBS but you can find them on line at Bike Tires Direct or Western Bike Works. I think Western has an online sale today on accessories 15% off. I was using my iPhone app Map My Ride with this case. Got a Garmin 500 now so I don't use the case but my wife uses hers yet.

http://www.westernbikeworks.com/prod...art-phone-case
http://www.biketiresdirect.com/produ...art-phone-case